DESCRIPTION: The long term goal of this investigation is to understand the role of the mitochondrial outer membrane in cellular phospholipid synthesis. In this project, attention will be focused on mitochondrial glycerophosphate acyltransferase, the first enzyme in the pathway of glycolipid synthesis. Previous results from this and other laboratories have indicated that this enzyme controls the quality of membrane phospholipids by selectively positioning fatty acids in cellular phospholipids. Dr. Haldar and his colleagues have purified the rat liver enzyme to homogeneity and have cloned and sequenced the cDNA. Their results also indicate the presence of a mitochondrial membrane protein which stimulates the acyltransferase. In this project, the stimulant protein will be purified, biochemically characterized and cloned. Its proximity to the mitochondrial glycerophosphate acyltransferase will be examined. Additionally, the mode of biosynthesis of the mitochondrial glycerophosphate acyltransferase will be investigated. The proposal includes determination of the initiator methionine, signal sequence and its nature and the topography of the mitochondrial GAT in the transferase plane of the mitochondrial outer membrane. These studies are expected to increase our knowledge on how mitochondrial glycerophosphate acyltransferase gene is regulated in the mammalian system.